An over the top (OTT) is known as a data delivery scheme capable of delivering content such as image data or audio data regardless of a service form of a telecommunications carrier. Delivery content based on the OTT is referred to as “OTT content,” and a delivery service of image (video) data using the OTT is referred to as an “OTT video” or an “over the top video (OTT-V).”
For example, a dynamic adaptive streaming over HTTP (DASH) is used as a fundamental technology of data streaming delivery according to the OTT-V. The DASH is a standard of an adaptive streaming technique using a hypertext transfer protocol (HTTP).
In the adaptive streaming, in order to enable various clients to reproduce delivery content, a content delivery server creates and holds segmented files of moving image content of a plurality of bit rates and a manifest file describing attribute information or a URL thereof.
The client acquires the manifest file from the server, selects optimal bit rate content according to a size of a display unit of its own device or an available communication band, and receives and reproduces selected content. It is also possible to dynamically change a bit rate according to a variation in a network band, and at a client side, it is possible to switch and receive optimal content according to circumstances as necessary, and moving image content reproduction in which the occurrence of video interruption is reduced is implemented. The adaptive streaming is disclosed in, for example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2011-87103).
An MPEG-DASH standard is known as a standard specifying a specification for performing streaming delivery of a moving image or audio data encoded by moving picture expert group (MPEG) according to the DASH.
The MPEG-DASH standard includes the following two standards:
(a) a standard related to a manifest file (media presentation description (MPD)) describing metadata serving as management information of a moving image or an audio file; and
(b) a standard related to a file format (segment format) for moving image content transmission.
When streaming delivery of MPEG data is performed according to the DASH, a process is performed according to the MPEG-DAH standard.
However, the DASH serving as the standard of the adaptive streaming technique is based on a point-to-point type HTTP streaming technique serving as a one-to-one communication process.
Thus, for example, when the DASH is applied to streaming delivery of content (a program) that is likely to be simultaneously viewed by a plurality of clients such as sports relay, support of content delivery network (CDN) is necessary.
However, there is a cost restriction to constructing the point-to-point HTTP streaming to which the CDN is applied, and it is difficult to implement scalability equal to broadcast delivery. As described above, the DASH uses a streaming protocol based on the HTTP and has a problem in that it is not adequate to content delivery that enables simultaneous viewing by a plurality of clients such as broadcast delivery.